In many imaging systems, such as imagesetters or platesetters, a movable optical carriage is used to displace a laser system or other imaging source in a slow scan direction along an internal drum to expose a supply of recording media supported on the drum. Generally, the imaging source includes a beam deflection assembly, comprising a deflector element (e.g., a mirror) and a spin motor for rotating the deflector element, for deflecting an imaging beam generated by a radiation source across the recording media. Such an imaging system is described, for example, in U.S. Pat. No. 5,598,739, assigned to the Agfa Division, Bayer Corporation, incorporated herein by reference.
Currently available internal drum imaging systems, such as the imaging system disclosed in U.S. Pat. No. 5,598,739, commonly utilize a two-piece internal drum comprising a base portion and an upper structure. The base portion is in the form of a partial cylinder and includes a machined imaging surface for supporting and positioning a supply of recording media during imaging. The upper structure is mounted on the base portion and includes a rail system for supporting and guiding a movable optical carriage along the length of the internal drum.
The base portion and the upper structure of the internal drum are separately cast from a lightweight material such as an aluminum alloy, and are separately machined and finished according to design requirements. Since the base portion and the upper structure comprise separate components, means for attaching the upper structure to the base portion under exacting tolerances must be provided. Thus, the separate manufacture and subsequent attachment of the upper structure to the base portion greatly impacts the expense and time required to produce and assemble a two-piece internal drum.
The imaging engine (i.e., the internal drum, optical carriage, electronics, cabling, etc.) of an internal drum imaging system is typically mounted on a frame structure using a plurality of vibration isolating mounts. The vibration isolating mounts, which are commonly located under the internal drum, support and isolate the imaging engine against shock and vibration from external sources during the operation, transportation, and storage of the imaging system. Although the vibration isolating mounts effectively isolate the imaging engine against most external sources, damage to the outer covers or "skins" of the imaging system, to the imaging engine itself, or to other components of the imaging system, often occurs due to excessive sway of the imaging engine within the frame structure. Such excessive sway of the imaging engine may occur, for example, in response to a large sudden jolt to the imaging system during shipping.